1. Field of the Invention
This invention relates to a light sensitive screen which employs as its photoelectric material an amorphous silicon film containing hydrogen.
The light sensitive screen is especially useful when applied to a photosensor which is operated in the storage mode, for example, a target for a photoconductive type image pickup tube or a solid-state imaging device.
2. Description of the Prior Art
Amorphous silicon containing hydrogen exhibits a photoconductivity and can form a thin film of large area at a comparatively low temperature, so that applications to the light sensitive screens of a solar cell, an imaging device etc. have been proposed. As a typical example of a photosensor which is operated in the storage mode, there is a photoconductive type image pickup tube.
It has been proposed and previously applied for a patent (U.S. Pat. No. 4,255,686) to use as the photoconductive layer of such image pickup tube an amorphous material whose principal constituent is silicon and which contains hydrogen.
A patent application (Ser. No. 066,230, HITACHI) has also been previously filed as to the application of the hydrogen-containing amorphous silicon to a solid-state imaging device which employs a photoconductor.
The hydrogen-containing amorphous silicon can readily provide a high resistivity. This is an advantage which is not inherent in materials having heretofore been used for light sensitive screens, for example, Sb.sub.2 S.sub.3 --, PbO-- and Se-based chalcogenide glasses. The advantage signifies that a charge pattern stored on the side of a light sensitive screen as is scanned by an electron beam does not decay within a storage time (the period of time which is taken for a specified picture element to be scanned by the scanning electron beam).
This invention further intends to improve various characteristics as imaging devices.
The following publications indicate the prior arts of this invention:
(1) Great Britain Pat. No. 1,349,351 PA1 (2) U.S. Pat. No. 4,147,667 PA1 (1) dark current characteristics PA1 (2) lag characteristics PA1 (3) after image characteristics PA1 (4) resolution